DMTCP-2.4.8 released

• The newest kernels (approximately Linux version 4.0 and later map
  VDSO into memory slightly differently for 32-bit processes running
  in a 64-bit Linux. DMTCP was failing to restart for such 32-bit processes.
  This is now fixed.
• dmtcp_dlsym() extended to provide more robust wrapper functions.
• Corner case fixed: signal handlers now restored before plugins restart.
• Minor bug fixes.